Under what circumstances Commissioner could direct the Officer to prefer an appeal against the order of the adjudicating authority

The Commissioner may, on of his own motion, or upon request from the Commissioner of State tax Commissioner of Union Territory tax, call for and examine the records of any proceeding in which an adjudicating authority has passed any decision or order under this Act or the SGST Act or the UTGST Act, for the purpose of satisfying himself as to the legality or propriety of the said decision or order. The Commissioner may by an order, direct any Officer subordinate to him to apply to the Appellate Authority within six months from the date of communication of the said decision or order for the determination of such points arising out of the said decision or order as may be specified by the Commissioner in his order.

(ICAI FAQ PUBLICATIONS 06-09-2017 APPEALS AND REVISIONS : FAQ NO. 4)

Who could prefer an appeal before the Appellate Authority

Following could prefer an appeal before the Appellate Authority:
(a) Any person aggrieved by the order or decision of the adjudicating authority
[FORM GST APL-01Chapter-XIII – Appeals and Revision of the CGST Rules]
(b) Any authorised officer on direction of the Commissioner (this is referred to as application and filed in FORM GST APL-03).

(ICAI FAQ PUBLICATIONS 06-09-2017 APPEALS AND REVISIONS : FAQ NO. 3)

Who is an adjudicating authority

Section 2(4) defines adjudicating authority to mean any authority appointed or
authorized to pass any order or decision under this Act. However, following are not covered under the ambit of adjudicating authority:
(a) Central Board of Customs and Excise (Board),
(b) Revisional Authority,
(c) Authority for Advance Ruling,
(d) Appellate Authority for Advance Ruling,
(e) the Appellate Authority
(f) Appellate Tribunal
Therefore, an order passed by any officer other than the revisionary authority as well as other authorities mentioned above could be contested before the Appellate Authority.

(ICAI FAQ PUBLICATIONS 06-09-2017 APPEALS AND REVISIONS : FAQ NO. 2)